For preparing a film of a tapered copolymer of styrene-butadiene or mixtures thereof

ABSTRACT

A tapered styrene-butadiene copolymer is extruded to form a film and a sheet. The tapered styrene-butadiene copolymer can be admixed with polystyrene and is extruded to form a film and is pressed or stretched. The tapered copolymer can be a copolymer of a molecular weight of 40,000 - 250,000 with a total styrene content of 60 - 90 weight percent and with a total butadiene content of 40 - 10 weight percent. More than 10% of the chain portion has a tapering rate of 0.3 - 4. The tapered styrenebutadiene copolymer consists of (a) more than 5% of the chain portion with a styrene content of 30 - 70 weight percent, (b) more than 35% of the chain portion with a styrene content more than 80 weight percent, and (c) more than 10% of the chain portion with a styrene content less than 50 weight percent. When the tapered copolymer of styrene-butadiene or mixtures thereof is extruded and stretched, the resulting transparent film has a high tear strength and impact strength. No white mar is formed when the film is torn or bent.

United States Patent [191 Horiie et al.

I Dec. 10,1974

[ PROCESS FOR PREPARING A FILM OF A TAPERED COPOLYMER OF STYRENE-BUTADIENE OR MIXTURES THEREOF [75] Inventors: Shigeki Horiie, Yokohama; Susumu Kurematsu, Zama-Machi; Shinichiro Asai; Chiaki Saito, both of Tokyo, all of Japan V [73] Assignee: Denki Kagaku Kogyo K. K., Tokyo,

Japan [21] Appl. No.: 294,832

[30] Foreign Application Priority Data Oct. 4, 1971 Japan 46-77154 Oct. 25, 1971 Japan 46-83960 [52] US. Cl. 264/210 R, 260/837, 260/942 M, 260/880 B, 264/92, 264/289 [51] Int. Cl. B29d 7/24, C08f 19/08, C08d 3/06 3,668,279 6/1972 Loveless et a1 260/942 M Primary Examiner-Jeffery R. Thurlow Attorney, Agent, or Firm-Oblon, Fisher, Spivak,

McClelland & Maier 7] ABSTRACT A tapered styrene-butadiene copolymer is extruded to form a film and a sheet. The tapered styrenebutadiene copolymer can be admixed with polystyrene and is extruded to form a film and is pressed or stretched. The tapered copolymer can be a copolymer of a molecular weight of 40,000 250,000 with a total styrene content of 60 90 weight percent and with a total butadiene content of 40 10 weight percent. More than 10% of the chain portion has a tapering rate of 0.3 4. The tapered styrene-butadiene copolymer consists of (a) more than 5% of the chain portion with a styrene content of 70 weight percent, (b) more than of the chain portion with a styrene content more than 80 weight percent, and (c) more than 10% of the chain portion with a styrene content less than weight percent. When the tapered copolymer of styrene-butadiene or mixtures thereof is extruded and stretched, the resulting transparent film has a high tear strength and impact strength. No white mar is formed when the film is torn or bent.

4 Claims, No Drawings PROCESS FOR PREPARING A FILM OF A TAPERED COPOLYMER OF STYRENE-BUTADIENE OR MIXTURES THEREOF BACKGROUND OF THE INVENTION 1. Field Of The Invention This invention relates to a process for preparing a film of a tapered styrene-butadiene copolymer or mixtures thereof which have a high tear strength and impact strength, and do not form a white mar when the film is bent or torn.

2. Description Of The Prior Art Biaxial oriented polystyrene films have been known which possess a very low impact strength. In order to improve the impact strength of these films, high impact polystyrene films fabricated from polystyrene and reinforced with elastomer particles have been prepared.

bsbsbsb bsbsbsbs However, these films are opaque or translucent because of the presence of the elastomer particles. In addition, these films form a white mar when they are bent.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a process for preparing a film of a tapered copolymer of styrene-butadiene or mixtures thereof which has an excellent tear strength and impact strength, and leaves no white mar when bent or torn.

This object and other objects of this invention can be achieved by providing a process for preparing a film of a tapered copolymer of styrene-butadiene or mixtures thereof by extruding a specific tapered copolymer to provide an orientation of the copolymer chains. The specific tapered styrene-butadiene copolymer consists of chains wherein the ratio of styrene monomer units to butadiene monomer units continuously changes. The tapered styrene-butadiene copolymer has a molecular weight ranging from 40,000 to 250,000, a total styrene content of 60 90 weight percent and a total butadiene content of 40 weight percent. More than 10% of the chain portion has a tapering rate of 0.3 4. The ta- 0 pered styrene-butadiene copolymer has (a) more than 5% of the chain portion with a styrene content of 70 weight percent, (b) more than of the chain portion with a styrene content more than 80% and (c) 5 more than 10% of the chain portion with a styrene content less than weight percent. The tapered styrenebutadiene copolymer can be admixed or melt-admixed with polystyrene.

[0 DESCRIPTION OF THE PREFERRED EMBODIMENTS In the chain of the tapered styrene-butadiene copolymer, the quantity of styrene relative to butadiene continuously changes as shown in the following schematic 15 structure. The reference numerals above the letters b and s designate the ratio of styrene (s) to butadiene (b) s o butadiene (b) to styrene (s) (b s).

sbsbsb bsbsbsbsbsbsbsbsbs 5 5 5 5 4 4 4 bsbsbsbsbsbsbsbsb The absence of a numeral above the letters indicate a styrene-butadiene ratio or a butadiene-styrene ratio of l 1. The chain portion with the tapering styrene- 50 ing structures, which are only a limited number of the types of combinations possible.

butadiene content is indicated by the abbreviation? 3 The letter c represents a coupler molecule or a catalyst which forms a branch in the polymer chain. Preferably, a low content of 1.2 vinyl bond units is maintained in the butadiene units of the micro-structure of the ta pered styrene-butadiene copolymer. It is especially pre ferred to maintain less than 30% 1.2 vinyl bond units to the total butadiene monomer unit content.

The tapered styrene-butadiene copolymer can be prepared by the living anion polymerization method which is disclosed in applicants copending US. Pat. application Ser. No. 134,39l, filed Apr. 15, 1971, now abandoned. The following reactions are typical methods for the preparation of the tapered styrenebutadiene copolymer:

(a)s-s-sb sbss Styrene is polymerized in the presence of an alkyl lithium catalyst in a non-polar hydrocarbon solvent such as benzene, cyclohexane, n-heptane or toluene. A mixture of butadiene and styrene is charged, after completion of the styrene polymerization reaction. Butadiene can be charged before completion of the styrene polymerization reaction. However, the tapering rate and the length of the tapering portion of the polymer chain are difficult to control by this process. Preferably, butadiene and styrene are separately charged to the reactor in the presence of a randomizer such as tetrahydrofuran, dimethyl ether, diethyl ether, anisole or amines, e.g., triethyl amine in order to control the ratio of butadiene to styrene. This procedure results in control'of the lengthof the tapering portion of the copolymer chain in the styrene-butadiene system.

(b)ss-bb sb sb ss Styrene is'polymerized in the presence of an alkyl lithium catalyst in a non-polar solvent. Butadiene is initially charged to the reactor after the polymerization of styrene, followed by a second charge of butadiene and styrene block rate butadiene and styrene to the reactor in the presence of Styrene is polymerized, and then butadiene and styrene I are charged to the reactor to form the tapering portion of the sb sb chain. Subsequently, butadiene is polymerized and the tapering portion of the sb sb chain is formed. This is followed by the addition Tap ering rate (70) Separated block styrene polymer (wt.)

and polymerization of styrene. The copolymer may also be prepared by charging butadiene and styrene to the reactor in the presenceof a dilithium catalyst.

(e)sb sb s ssb .rh ss Styrene and butadiene are charged twice to a reactor in the presence of a non-polar hydrocarbon solvent containing an alkyl lithium catalyst. A multi-tapered copolymer can be prepared by repeating this process.

(f) sb sb sb Styrene and butadiene are charged to a reactor in the presence of a non-polar hydrocarbon solvent containing a dilithium catalyst and a small amount of a randomizer or in the presence of a randomizer containing an alkyl lithium catalyst. The formation of the copoly' mer is influenced by control of the ratio of butadiene to styrene charged to the reactor.

(g)sb sb bb sb Sb Butadiene is polymerized in a non-polar hydrocarbon solvent containing a dilithium catalyst, and then styrene and butadiene are charged to a reactor in the presence of a small amount of a randomizer while controlling the ratio of styrene and butadiene charged to the reactor. Styrene and butadiene may also be polymerized in the presence of a randomizer and an alkyl lith ium catalyst.

The sb sb tapered copolymer is prepared by charging styrene and butadiene to a reactor in the presence of a non-polar hydrocarbon solvent containing a lithium catalyst and a small amount of a randomizer. Tapered copolymer chains are coupled by a coupler such as trichloro monomethyl silane, trichloro monoethyl silane, tribromomethane or tribromoethane.

The sb sb tapered copolymer is bonded to a block styrene polymer and then coupled with a coupler. Various types of tapered copolymers may also be prepared by the use of a multi-functional coupler.

The amount of block styrene polymer can be measured by decomposing the tapered copolymer in the presence of a t-butyl hydroperoxide and osmium tetrachloride catalyst. Theh amount of separated block styrene polymer is determined by the following equation:

Totalcopolymer (wt.) x lqO The amount of block styrene polymer can also be measured by infrared spectral measurements at 540 cm.

The tapering rate of the polymer can be calculated by measuring the conversion rate and the styrene content at certain stages during the copolymerization reaction. The difference in the styrene content at two points in the chain is calculated, and the tapering rate is given by the following equation:

Difference in the styrene content at two points in the chain Percentage of the weight of the chain portion to the weight of the total chain The structure of the tapered styrene-butadiene copolymer can be confirmed by the calculated tapering rate. The tapered styrene-butadiene copolymer should have a molecular weight of 4,000 250,000 in order to have excellent transparency, and impact strength characteristics, as well as the ability to resist formation of white mar and micro-cracks when the tapered copolymer is processed to form films. The term film means a film or' sheet in any form. A lower molecular weight results in a copolymer with an inferior impact strength. A higher molecular weight copolymer results in inferior processing of the copolymer, especially as it relates to the formation of the unflown portion in the T-die. In addition, rough surfaces and low transparency arise during the inflation processing of the high molecular weight copolymers. The total styrene content of the tapered copolymer is preferably in the range of 60 90 weight percent. A lower styrene content results in a rubberlike product which has no advantages over conventional block copolymers. A styrene content greater than 90 weight percent results in a copolymer with a low impact strength, and a copolymer which forms micro-cracks when bent. Preferably, the copolymer chain contains more than 5% of a chain portion which has a tapering rate of 0.3 4 and a 30-70 weight percent styrene content. When the chain portion containing the tapering portion is lower than 5%, the impact strength is too low indicating that the styrene content should be decreased. The resulting film or sheet has a rubber-like property with rough surfaces and low transparency.

The tapered copolymer should contain a chain portion with a styrene content of at least 5% (but less than 50 weight percent styrene) between the two high styrene content chain portions which have a styrene content greater than 80 weight percent. This is referred to as the specific tapered structure. When a tapered styrene-butadiene copolymer does not possess-this specific tapered structure, it has lower impact strength and elongation characteristics. When the tapered styrenebutadiene copolymer possesses the indicated specific tapered structure, it has high impact strength and elongation characteristics. In addition, the copolymers resist the formation of cracks when bent as well as possessing other attendant advantages over conventional styrene-butadiene block copolymers. Even though an s s sb sb sb s s type tapered copolymer is admixed with an sb sb s s type tapered copolymer, the transparency, impact strength and elongation of the resulting composition are not substantially decreased. Accordingly, even though certain portions at the ends of the living polymer are inactivated by the polymerization process, the resulting polymer has no opaqueness as does the conventional block copolymer. When the tapered styrene-butadiene copolymer of this invention is formed as a thin film with its associated orientation of molecules, it possesses remarkable impact strength, especially against slow impact.

When the tapered styrene-butadiene copolymer is formed as a film less than 2 mm. thick, the film possesses remarkable characteristics such as a remarkable impact strength. The tapered styrene-butadiene copolymer can be formed without adding any plasticizer. Polystyrene may also be added to the tapered copolymer as it is formed into a film. The films and sheets prepared from the tapered styrene-butadiene copolymer or a mixture of the tapered copolymer with polystyrene, has all of the characteristics of a styrene film with improvements in transparency and impact strength. In addition, the copolymer does not form a white mar on bending or impact.

The process by which the films and sheets of the ta- 5 pered styrene-butadiene copolymer or mixtures thereof of this invention are formed are not limited. These processes include known processes such as the T-die extrusion method, the inflation method, the calender method or the casting method. The characteristics of the films and sheets of the tapered styrene-butadiene copolymer or of the copolymer mixtures with polystyrene are as follows:

Excellent transparency and surfacev luster. High mechanical strength, e.g., impact strength,

tear strength and bending strength.

No white mar or cracks are formed upon bending or impact. No moisture adherence and an excellent water repellency. The film does not change in length when subjected to a change in moisture. It is also dimensionally stable. @Suitable moisture and gas permeability. @No taste, no smell and no toxicity (no plasticizer is required).

@l-Iighly resistant to acid, alkali and aliphatic hydrocarbons, e.g., gasoline. Excellent electric characteristics.

Excellent secondary processing characteristics (vacuum forming, pressure forming, cold processing, bending, cutting, heat sealing, adhesion, metallizing). The tensile and impact strength do not decrease upon secondary processing with heat. 3 5 Good printability.

Heat shrinkable films can be formed.

The films and sheets of this invention can be used for a variety of applications, especially for packaging various foods. The films and sheets of this invention can be 40 laminated while retaining their excellent transparency,

surface luster and tear strength characteristics. A sheet of the tapered copolymers of this invention can be stretched by the application of pressure or a vacuum to the sheet with heat on a mold. The sheet conforms to the shape of the mold and gives rise to products such as cups and other containers.

Having generally described the invention. .1 further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified.

EXAMPLE 1 The following five types of tapered styrene-butadiene copolymers were prepared in the presence of an alkyl lithium catalyst in a non-polar solvent at various ratios of styrene to the total monomer content. The resulting copolymers were extruded as films. The ratio of styrene to the total monomer content was 85 or 70% and the results are shown in Tables I, IV and VII. The type I tapered copolymer had the structure: s s sb sb s s, and was prepared by process (a). The type ll tapered copolymer had the structure: s s sh sh sb s s, and was prepared by process (0). The type III tapered copolymer had the structure: .r s sb Sb), 0, and was prepared by process (i).

Referencel:ssb-bss The reference s s b b s s block copolymer was preparedby polymerizing styrene in a non polar hydrocarbon solvent in the presence of an alkyl lithium catalyst. This was followed by polymerization EXAMPLE 2 A tapered styrene-butadiene copolymer or a block copolymer was admixed with polystyrene of a 160,000 number average molecular weight and a 320,000

Number of average b ff bi i i weight average molecular weight together with 0.25 Q f' i b1 k 1 weight percent of the anti-oxidant, 2,6-di-t-butyl-4- l L ence )30 9 copo ymer methyl phenol. The mixture was pelletized in a screw was prepared by polymenzmg Styrene m a non-polar t xtruder with a 20 mm diameter The characterishydrocarbon solvent in the presence of an alkyl lithium l d h catalyst. This was followed by polymerization with bu- 10 0 the mixed 9 ystyrene copo ymer an t e tatadiene and coupling of the product with a tripared styrenetblnadlene cOPOlymer ware measured function a1 coupler. The characteristics of the mixture are shown in Tables X and XI. The mixed polystyrene copolymer and the Fflm formati0n process-es tapered copolymers of this invention can be processed as films which possess excellent physical characteris- (A) T-die method i In Tables X and XI: I A tapered styrene-butadiene copolymer or a refer- A A 3 s b b s s type copolymer. ence block copolymer was melted and extruded from B,, B s s sb sb s s type copolymer. a T-c lie extruder. The extruded material was pressed by C1 C2 3 S s Sb Sb Sb s s type a pair of rolling rollers, transferred through guide rolpolymer lerskand WT(')Lll'ld to yield a smooth sheet of uniform Total Styrene content was measured by NMR thic ness. he sheet possessed a specific molecular orientation. The conditions for the film forming processes g ggi r i moleculartgeldghts were measured .are shown in Table II wherein the roller pressure ranges lfjretssure g; 1 l from 0.25 to 25 kg cm. Tear strength, elongation, ime amoun O S yiene 06 p0 imer meapact strength, hardness, cloudiness and white mar of Sued by de.composmg t copolymer.wlth t'butyl the polymer were measured. These results are shown in hydroperoxlde and tetrachloride Table I. The thickness, tensile strength, elongation, @The rate of each Cham portion to h total cham breaking strength, tear strength, Elemendolf tear, was measured by h curve. of chain length and thrust, bending resistance, strength and heat shrinkage the styrenebuladlens ratio whlch calculaled properties of the film formed under the conditions I from the f f rate from Samples taken durmg listed in Table II are shown in Table III. the Polymerization @Tensile strength and elongation were measured by a Damble type test piece havin a thickness of 2 (B) lnflatmn method @mm, a width of I0 mm, and a le ngth of 80 mm.

. l Impact strength was measured by a DIN method, The tapered styrene-butadiene copolymer shown in Table IV was processed by the inflation method to form g test piece 2 mm a FT. wide a film. In the process, the molten copolymer was exi j was measure y t e M43485 truded from an annular slit havin a 0.5 m a to form a tube. A Specific amount air g to @Cloudmess was measured by the ASTM-D-l003 stretch the film. The tubular film was solidified with l cooling air from a cooling ring, and taken up through ensrle strength and elongation were measured by the guide rollers and knip rollers. The thickness and the Japan lndusmal Standard K'6872 method width of the film were determined by the die pressure, (D strength was measured by the Japan lndusmal extrusion rate, take-up speed and air blow rate. Differ- Standard K4732 methodent thicknesses of the films were determined by cali- Elemend0lf tear was measured y the Japan Indusbrated positions of the cooling ring. The take-up speed mal standard 1L8] 16 methodranged from 3 to 8 m/min and the diameter stretch rate must was measured y 3 mm impact testerwas 2 5. Films possessing uniform thickness and high Bending resistance Strength was measured y strength were produced by this process. The condition bending both Sides of a Sample to 3 angle with for film formation processes are shown in Table v. The a 3 kg weight, and calculating the number of times characteristics of the resulting films are shown in Table the Sample is bent until it is Severed- @Heat shrinkage was measured by heating in an oven.

(C) T-dre method @Dart drop impact strength was measured by dropping the rod with a spherical top (R=l .5 cm) from The tapered styrene-butadiene copolymer shown in a 50 cm height. Table VII was processed according to the (A) T-die @Permeability was measured by the Japan Industrial method to form sheets. The conditions for the sheet Standard Z-0208 method. forming processes are shown in Table VIII, while their Gas permeability was measured by the AST- characterstics are shown in Table IX. M-O-l434-58 method.

TABLE I Type I Type II Ty e III Refer nce I Reference II Type of Polymer (D (2) (ID G5 Total Styrene content (a) 85.3 85.l 84 5 85.7 84.8 85.8 85.0

TABLE I Continued Type 1 Type 11 Ty 111 Reference 1 Refer nce 11 Type of Polymer (D s molecular we1ght( 10) (b) 15.2 14.8 15.3 15.0 15.6 14.7 15.8 Styrene block rate (c) 71.5 62.5 61.0 62.0 62.5 85.2 85.3 Rate of chain portion with a tapering rate of 03-4 and a styrene content of -70 weight percent (d) 11.5 20.3 20.5 20.5 20.3 Rate of chain portion with more than an wt. styrene content (d) 76.5 71.1 72.3 71.4 71.6 85.2 85.4 Rate of chain portion with less 7 than a 50 wt. styrene content (d) 17.0 13.6 14.5 13.5 13.6 15.1 15.0 Tensile strength (kglcm (e) 377 360 345 352 366 401 393 Elongation (e) 91 107 117 44 39 Impact strength (kg/cm) (f) 89 100 1 10 97 103 31 36 Hardness Rockwell R-scale (g) l 17 105 101 1 10 1 12 127 129 Cloudiness (h) 6.4 5.2 7.1 4.7 5.3 6.4 5.8 White mar by bending none none none none none cracks cracks TABLE 11 Condition of Temperature of .cylinder Temperature Amount C.) T-die Screw of roller C.) Roller of ore Speed of rotation, rotation trusion takenp Experiment number Polymer C1 C2 C C4 C D1 D2 D3 r.p.m. R1 R1 R3 (r.p.rn (kg./hr.) (rm/mint.)

NOTE.Extruder with a 40 mm. vent-attach (L/D 22 screwpitch 40 mm.) was used. Physical properties of the sheet are shown in Table III.

TABLE III P01yn1er- Type I Type II Type III Reference 1 Reference 11 Lon- Hori- Lon- Hori- Lon- I-Iori- Lon- Hori- Lon- Hori- Lon- Hori- Lon- Horigitu' zongituzongituzongituzongitu zongituzongitnzon- Direetion dinal tal dinal tel dinal tal dinal tal dinal tal dinel tal dinal tal Average thickness (mm). 0. 97 1. 01 0. 94 1. 02 0. 95 0. 93 0. 96 1. Cl 0.95 0. 97 0. 97 0. 99 0. 97 1.01 Tensile test (i):

Yield strength (kg.

mm! 4. 2 4. 0 3. 8 3. 6 3. 9 3. 5 3. 0 3. 6 3. 7 3. 5 4. 6 4. 4 4. 7 4. 4 Elongation (percen 70 64 120 110 110 90 108 98 108 05 20 18 1.) 17 Braking strength Tear strength (kg/mm!) (1' 10. 3 10. 1 13. 8 13. 2 14. 6 13. 1 14. 7 13. 9 14. 4 13. 0 3. 8 3. 6 4. 0 3.1) Elemendolf tear strength (g.) k 3, 200 2, 90 3. 200 3, 200 3, 200 3, 200 3. 203 3, 099 3, 200 3, 200 450 380 430 390 Thrust (kg. cum/111m.) (1) 7. 8 7. 8 8. 4 8. 4 8. 0 8. 0 8. 8 8. 8 8. 5 8. 5 3. 2 3. 2 3. 0 3. 0 Bending resistance strength (3 kg. weight terms) (In) 87 73 134 62 123 84 110 90 144 14 20 16 21 Heat shrinkage (percent 1 minute) (n) -2s 7 30 6 30 5 20 5 32 6 9 7 8 TABLE IV Type 1 Ty e 11 T 111 Reference 1 Refer nce 11 Type of Polymer Q) Total Styrene Content (a) 80.4 79.5 80.0 80.2 79.8 79.8 80.5 Number average molecular weight (X 10) (b) 12.4 13.1 11.9 13.0 13.7 11.9 13.5 Styrene block rate (c) 67.0 55.5 55.0 55.0 54.5 80.0 79.0 Rate of chain portion with a tapering rate of 0.3-4 and a styrene content of 30-70 wt.(%) (d) 11.4 20.3 19.1 21.0 19.8 Rate of chain portion with more than an 80 wt.(%) styrene content (d) 70.3 65.2 64.9 65.7 64.9 80.5 79.0 Rate of chain portion with less than a 50 wt. styrene content (d) 24.0 21.1 22.7 20.1 18.9 19.5 21.0 Tensile strength (kg/cm) (e) 320 298 295 300 302 350 362 Elongation (e) 110 149 150 145 146 69 62 Impact strength (kg/cm) (1) 128 142 145 145 139 55 52 Hardness Rockwell R-scale (g) 108 97 94 98 98 1 19 123 Cloudiness (h) 6.0 5.3 4.0 4.7 5.1 5.7 6.4 White mar by bending none none none none none cracks cracks TABLE V Condition Amount 'lotnl Temperature of cylinder C.) T-die Screw of Take-11p 111111. 1 1911- Experirotation, extrusion speed of gnlmn ment N0. Polymer C1 C2 C3 C4 C5 D1 D2 D1 r.p.m. (kg/hr.) (UL/111111.) Stretch blow mtv. (D 140 150 160 160 170 170 180 180 6. .2 5 7. 3 2. 2. 115. 1 (D 150 162 165 165 170 170 180 180 40 5.!) 5 7.1 2.1- 11.0 140 160 165 165 170 175 185 185 50 6. 7 6 G. 8 2. 4 1b. 3

TABLE VI,

Polymer 01- Type I Type II Type 111 Reference 1 Reference 11 (D 6) Longi- Hori- Longi- Hori- Longi Hori- Longi- 1Iori- Longil1ori- Longi- 1[ori- Lough 1101+ IN-011011 tudinnl zontnl tndinnl zontnl tudinnl zontnl tudlnnl 1.0111111 tudimil 7.0111111 11111111111 znntul Ludinul 7.011111 1 rag t i ss (11) 38 38 v 42 42 43 43 41 41 15 1s 37 37 12 Tens11e test Yieldzstrength(kg/mm?) 2. 7 2. 4 2. 4 2. 1 2. 5 .2. 2 2. 4 2. 3 2.. 3 .Z. l 3 0 2.11 3 1 J. H Elongation (percent)- 200 170 230 220 240 210 210 220 .225 210 5a 52 '11 51 Breaking strength (kg./mm.'-') 2.1 1.9 2.2 2.1 2.4 1.9 2.3 2.0 2.2 1. 2.9 2.8 3.0 2. 7 Tear strength (kgJrnm (1 7. 8 5.8 8. 2 6.5 8 0 6.1 7. 8 6. 3 7. .1 6. 2 5. 2 4. 3 5.3 1. 5 Elemendolf tear 33 51 36 4 30 37 45 30 8 5 7.6 8. 2 7. 3 Thrust (kg. omlmm.) (1) 17. 2 17. 2 20. 5 20. 5 20. 1) 20. J 10. 5 10 5 19. 0 19. 0 6. 5 6. 5 7.0 7. 0 Dart drop impact strength y/ 0) H5 115 120 110 110 115 115 s. 0 0 7. 0 7 0 Permeablhty (g. mmJrnfl/m 1. 5 1 1. 54 1. 55 1. 56 1. 59 1. 50 1. 52 1. 52 1. 53 1. 57 1. 57 50 1. 511 1). 47 E). 47 J. 40 0. 40 1 J. 57 .1. 57 .J. 31 .1. 31 J. 52 1 5" 1. 61) 11.60 1 5] 1. 5E)

TABLE V11 1 Type I Type 11 Ty 111 eferenc Type of Polymer 6) Total Styrene Content (a) 70.4 70.8 69.9 70.2 70.5 70.5 70.4 Number average molecular weight (X 10 (b) 9.1 8.8 8.5 9.0 10.2 8.9 9.7 Styrene block rate (c) 57.5 39.5 1 47.5 40.0 40.5 709.2 70.6 Rate of chain portion with a tapering rate of 0.3-4 and a styrene content of 30-70 wt.(%) (d) 6.3 25.8 12.4 25.3 26.0 Rate of chain portion with more than a 30% wt.(%) styrene content (d)- 61.0 51.7 54.1 52.2 51.5 70.2 70.9 Rate of chain portion with less than a 50 wt.(%) styrene content (d) 35.6 29.6 36.5 30.2 29.5 30.1 31.0 Tensile strength(kg1cm) (e) 153 132 135 200 195 Elongation (e) 360 420 450 400 450 210 210 Impact strength (kg/cm) (2) 150 150 150 150 85 90 Hardness Rockwell R-sca1e (g) 39 28 3O 32 31 S5 54 Cloudiness (h) 12.2 10.6 11.7 11.5 12.4 11.5 11.2 White mar by bending none none none none none none none TABLE VIII Condition of Temperature of cylinder 'lemperature of roller C.) T-die Screw 0.) Rollo! Amount 01 Speed of Exportmont rotation, rotation, extrusion take-11p No. Polymer C1 C: 0-; (3| C D; D D3 1'.p.m. R1 R2 R3 (1'.p.n1.) (kg/hr.) (nL/min.)

as set forth herein.

Accordingly what is claimed as new and intended to be covered by letters patent is:

TABLE IX Polymer of T e I T e 11 yp yp Type III Reference I Reference II (D (D (D (D Direction Lon- Lon- Lon- Lon- Lon- Lon- Longitu- Horigitu- Horigitu- Horigitu- Horigitu- Horigitu- I'Iorig1tu- Horidinal zontal dinal zontal dinal zontal dinal zontal dianl zontal dinal zontal dinal zontal Average thickness (p) 0.98 0. 98 0.99 0.99 0.97 0.97 1.10 1.10 0. 90 0.99 0.98 0. 98 1.00 1.00 Tensile test (i);

Yield strength (kg/111111. 1.5 1.3 1.3 1.1 1.3 1.2 1.4 1.1 1.3 1.2 1.8 1.6 1.9 1.7 Elongation (percent) 350 330 420 400 440 410 430 420 410 400 230 210 210 200 Breaking strength (kgJrnmI 1.4 1.2 1.2 1.1 1.2 1.0 1.3 1.1 1.0 1.1 1.7 1.4 1.7 1.5 Tear strength (kg/mm!) (1'). 12.4 11.6 15. 2 14.8 15. 6 15.2 14.9 15.1 15.5 15.0 10.5 10. 2 10. 6 10. 1 Elemendoli tear strength (g.) (k) 3, 200 3, 200 3, 200 3, 200 3, 200 3, 200 3, 200 3, 3, 200 3, 200 1,100 1,000 1, 200 1,100 Thrust (kg./cm./mm.) (l)... 8.6 8.6 9.3 9.3 9.8 9.8 9 6 9.6 9.9 9.) 5.3 5.3 5.6 5.6 Bending resistance strength (3 kg. Weight terms) (111).- 662 681 752 773 781 742 765 789 758 771 232 245 273 281 Heat shrinkage (percent 1 min.) (11) 21 '4 24 3 26 5 23 4 6 -20 3 -22 4 TABLE X Block Tapered Tapered copolycopolycopoly- Polymer mer mer ISt: A1 PStIBr PSt: Cr PSt: B1 PSt: C1 Type of polymer styrene (A1) (B1) 0|) =1:1 =1:1 =1:1 .1 =2:1

Total styrene content (a) 100 80 80 80 90 90 90 98. 3 93. 3 Number average molecular weight (X10 (b) 16 10. 5 10. 3 Styrene block rate (percent) (0) 100 80 67 Rate of chain portion with a. tapering rate of 0.3-4

and a styrene content of 30-70 wt. (percent) (d) 0 0 33 Rate of chain portion with more than an 80 wt.

(percent) styrene content (d) 100 80 Rate of chain portion with less than a 50 wt.

(percent) styrene content (d) 0 20 28 Tensile strength (kgJcmJ) (e). 456 380 330 Elongation (percent) (e) 4 105 Impact strength (kg/cm.) 8 31 89 Hardness Rockwell R-scale (g 65 41 31 Cloudiness (percent) (h) 4. 0 7. 8 8. 0 6. 5 9. 5 7. 0 5. 5 6. 5 5. 7 Whlte mar by bending Broken Cracks None None Broken None None Cracks None TABLE XI Block Tapered Tapered Polycopolymer copolymer copolymer IStzA2 PSVB; PSt-CQ IStzBz PStZCr Type of polymer sytrene (A2) (B2) (C2) =4zl =1 1 =1 1 Total styrene content (a) 100 60 60 6 92 92 92 80 Number average molecular weight (X10 (b) 16 8. 0 7. 9 7. 7 Styrene block rate (percent) (c) 60 51 38 Rate of chain portion with a tapering rate of 0.3-4

and a styrene content of 30-70 wt. (percent) ((1)... 0 0 49 60 Rate of chain portion with more than an 80 wt.

(percent) styrene content ((1) 100 60 51 45 Rate oi chain portion with less than a 50 wt. (percent) styrene content (d) 0 40 47 53 Tensile strength (kgJcmA) (e) 456 252 237 221 442 440 415 332 315 Elongation (percent) (e) 4 700 900 900 13 25 45 112 impact strength (kg./crn.) (i). 8 15 35 45 75 89 Hardness Rockwell R-soale (g) 65 45 43 38 23 21 Cloudlncss (percent) (h) 1. 0 15.0 13. 5 11. 5 80 55 20 61 22 hite mar by bending Broken None None None Mar None None None 1 Small mar.

Having now fully described the invention, it will be 1. A process for producing a film or sheet from a taapparent to one of ordinary skill in the art that many pered styrene-butadiene copolymer or mixture thereof changes and modifications can be made thereto withwhich comprises melt-extruding through a T the exout departing from the spirit or'scope of the invention 65 truder wherein the temperature of the cylinder of the extruder is to 200 and the temperature of the die 'is from to 220 and stretching at a stretch roller pressure of 0.25 to 25 Kg/cm a tapered styrenebutadiene copolymer with a molecular weight of 40,000 250,000, a total styrene content of 60 90 weight percent, and a total butadiene content of 40 10 weight percent, wherein said tapered styrenebutadiene copolymer contains: (a) more than of the chain portion having a tapering rate of 0.3 4 and a styrene content of 30 70 weight percent, (b) more than 35% of the chain portion with a styrene content of more than 80% by weight, and (c) more than of the chain portion with a styrene content from at least 5 weight percent to less than 50 weight percent between high styrene content chain portions which have a y ne em isreate t e. 9 weisbtaewepy 2. The process of claim 1, wherein said meltextruding and stretching is conducted by the T-die method whereby a bi-axial orientation is imparted to the tapered copolymer.

3. The process of claim 1, wherein said tapered styrene-butadiene copolymer is admixed with polystyrene together with an anti-oxidant and the mixture is meltextruded and stretched by a T-die method.

4. The process of claim 1, wherein said tapered styrene-butadiene copolymer or a mixture of the tapered copolymer and polystyrene is melt-extruded and stretched to form a film less than 2 mm thick, 

1. A PROCESS FOR PRODUCING A FILM OR SHEET FROM A TAPERED STYRENE-BUTADIENE COPOLYMER OR MIXTURE THEREOF WHICH COMPRISES MELT-EXTRUDING THROUGH A T DIE EXTRUDER WHEREIN THE TEMPERATURE OF THE CYLINDER OF THE EXTRUDER IS 140 TO 200* AND THE TEMPERATURE OF THE DIE IS FROM 170* TO 220* AND STRETCCHING AT A STRETCH ROLLER PRESSURE OF 0.25 TO 25 KG/CM2 A TAPERED STYRENE-BUTADIENE COPOLYMER WITH A MOLECULAR WEIGHT OF 40,000 - 250,000, A TOTAL STYRENE CONTENT OF 60 - 90 WEIGHT PERCENT, AND A TOTAL BUTADIENE CONTENT OF 40 - 10 WEIGHT PERCENT, WHEREIN SAID TAPERED STYRENE-BUTADIENE COPOLYMER CONTAINS: (A) MORE THAN 5% OF THE CHAIN PORTION HAVING A TAPERING RATE OF 0.3 - 4 AND A STYRENE CONTENT OF 30 - 70 WEIGHT PERCENT, (B) MORE THAN 35% OF THE CHAIN PORTION WITH A STYRENE CONTENE OF MORE THAN 80% BY WEIGHT, AND (C) MORE THAN 10% OF THE CHAIN PORTION WITH A STYRENE CONTENT FROM AT LEAST 5 WEIGHT PERCENT TO LESS THAN 50 WEIGHT PERCENT BETWEEN HIGH STYRENE CONTENT CHAIN PORTIONS WHICH HAVE A STYRENE CONTENT OF GREATER THAN 80 WEIGHT PERCENT.
 2. The process of claim 1, wherein said melt-extruding and stretching is conducted by the T-die method whereby a bi-axial orientation is imparted to the tapered copolymer.
 3. The process of claim 1, wherein said tapered styrene-butadiene copolymer is admixed with polystyrene together with an anti-oxidant and the mixture is melt-extruded and stretched by a T-die method.
 4. The process of claim 1, wherein said tapered styrene-butadiene copolymer or a mixture of the tapered copolymer and polystyrene is melt-extruded and stretched to form a film less than 2 mm thick. 